Over the last forty years or so a number of sewer cleaning processes and machines have been developed to replace a system which had been employed for many decades. That process involved the cleaning of sewer lines by dragging buckets through them. Tripods were placed above adjacent manholes and a cable was fed manually between the manholes and through the laterals. Buckets were attached to the cable and dragged through the sewer lines by a motor and winch.
This very old sewer cleaning process has numerous disadvantages. The process was very labor intensive and involved the difficult step of inserting the cable between adjacent manholes. Moreover, the buckets did not effectively clean laterals which were substantially larger than the diameter of the buckets, and buckets cannot easily be pulled past obstructions in the sewer, such as roots or broken pieces of the sewer pipe.
Before proceeding with a description of further prior art, it will be helpful to briefly describe a typical sanitary sewer system for purposes of illustrating not only the prior art but the sewer cleaner of the present invention. A manhole is typically found at or near the intersection of cross streets. The manhole itself is usually cylindrical in shape and is the junction for four sewer laterals which typically enter the manhole at 90.degree. angles with respect to each other. Two or three of the laterals are sloped downwardly toward the manhole and enter the manhole at or near its bottom. The other lateral(s) typically leave the manhole and slope downwardly toward another remote manhole. The discharge laterals also leave the manhole at or near its bottom. An entire city or suburban sewer system may be interconnected by laterals and manholes and the slope is selected so that all sewage eventually reaches a sewage treatment facility. Storm sewer systems are similar to that just described but include a catch basin instead of a manhole. The catch basin usually includes a sump below the entrance of the laterals.
To clean such sewer systems and overcome the difficulties of mechanical removal of debris using buckets, several types of sewer cleaning procedures have been developed and are described in the patent art. On Nov. 6, 1883, U.S. Pat. No. 287,811 was issued to Dougine for "Cleaning Sewers." This patent describes a combination water injection and water pumping machine for flushing a sewer with water and removing the water and collected debris from settling chambers associated with the sewer lines.
More recent developments are described in Parmelee's U.S. Pat. No. 3,600,225 issued Aug. 17, 1971 for "Pipe Cleaning" and Shaddock's U.S. Pat. No. 3,658,589 issued Apr. 25, 1972 for "Catch Basin and Sewer Pipe Cleaner." In both of these patents, water under pressure is injected into sewer laterals through specially designed nozzles to wash debris into a manhole or catch basin.
The nozzles employed in the latter two patents are of a kind known for many years in the sewer cleaning art and include a threaded portion for being coupled to a water hose. The nozzles have a plurality of water jets, the jets being oriented so that after the nozzles are inserted into the sewer line, the jets are directed backwardly toward the catch basin or manhole. When water under pressure is supplied through the hose, the openings create water jets to force the nozzle up into the sewer lines. When the nozzle is retracted, the water jets further clean the sewer by a knife-like action and the additional water flushes loosened debris toward the catch basin or manhole.
The Parmalee and Shaddock patents differ primarily in the water injection and water recovery systems. In Parmalee, a screen is placed over a water recovery hose and water is pumped from a manhole into a settling tank, through a grit remover and centrifugal separator to a storage tank for being reused in the cleaning process. Parmalee does not include a vacuum system for removing large solids from the manhole. Shaddock on the other hand, employs a vacuum system for pneumatically conveying debris and water from the catch basin into a material collection chamber.
While these two patents disclose machines which represent significant improvements over the aforementioned bucket cleaning system, they still have several significant disadvantages. Parmalee's system of water reclamation is not employed with pneumatic or vacuum loading. Shaddock's device, on the other hand, must be reloaded with water at the beginning of each cleaning operation, or sewer cleaning must be carried out at a location near a water supply, such as a fire hydrant or water main. This deficiency results in extended downtimes, inconvenience and loss of overall efficiency. A sewer cleaning machine which overcomes these problems would be a significant advance in this technology.